P0505 and P0138

[Elias123]

Hello!

My Jeep Wrangler TJ is misfiring. It happens a few minutes into the trip and lasts for about 5 seconds. The RPM drops and there is a banging sound in the exhaust. I get error codes P0505 (Idle control system) and P0138 (02 sensor). I have cleaned the IAC sensor, but that didn't help. Is this due to the O2 sensor, or could it be something else?

 

[Chris]

Hello!

My Jeep Wrangler TJ is misfiring. It happens a few minutes into the trip and lasts for about 5 seconds. The RPM drops and there is a banging sound in the exhaust. I get error codes P0505 (Idle control system) and P0138 (02 sensor). I have cleaned the IAC sensor, but that didn't help. Is this due to the O2 sensor, or could it be something else?

Since you've already cleaned the IAC sensor and it hasn't resolved the issue, there might be a few other things to check.

The P0138 code points to an issue with the O2 sensor, specifically that it's reading a high voltage. A failing O2 sensor can affect how the engine runs by providing incorrect data to the PCM, which in turn can lead to poor fuel mixture and potentially misfiring.

Here are a few steps you should take:

1. Inspect the wiring and connection to the O2 sensor for any damages or corrosion. I can't stress this enough!
2. If the wiring looks good, consider replacing the O2 sensor itself, as it may not be providing accurate readings anymore.
3. Since you're also getting a code for the idle control system, make sure to check for vacuum leaks or other issues in the intake system that could affect idle quality.
4. Sometimes fuel injectors can cause misfires as well, so it might be worth having those checked.

 

[macleanflood]

Can you read live ODB data?

A $30 Bluetooth dongle and Torque Lite will do it.

In this case my front O2 is working correctly and my rear is over .9v and staying steady...good sign of failure.

-Mac